1. Field of the Invention
The present invention relates to the provision of a common heatsink for multiple chips and modules which are spaced apart on electronic packages, and to an arrangement for the formation of precision gaps between two or more chips or modules covered by a common heatsink. Furthermore, the invention is directed to the provision of a method for the production of a common heatsink for multiple chips and modules for electronic packages facilitating the formation of compliant thermal interfaces between a plurality of chips and a common heatsink with minimized effects of package tolerances.
In the electronic package technology, it is of extreme importance to be able to provide heatsinks, such as in the nature of plate-shaped caps or cover structures which are positioned over the semiconductor chips or other modules or leaded components of electronic packages, in order to maximize the dissipation of heat which is generated during operation, and reduce the deleterious effects thereof on reliability and functioning of the package.
Frequently, in the current state of the electronic packaging manufacturing technology, the manufacture, handling, and costs and aesthetic aspects are directed to the positioning of a single heatsink over a plurality of heat sources, such as the semiconductor chips and modules of the electronic packages. Potential variations in module heights and the elevations of the various chips which may differ relative to each other when mounted on the package substrates, necessitates the need for extremely thin thermal interfaces, and wherein there are encountered thermal expansion mismatches, which upon occasion renders impossible the ability of attaining the use of a single rigid heatsink for a plurality of chips and modules. Accordingly, it is an important aspect of the electronic package manufacturing technology to be able to provide common heatsinks for pluralities of chips and modules which will take cognizance of mismatches in height caused by the encountered thermal interfaces and thermal expansions.
Although the prior art to some extent concerns itself with the use of various types of heatsinks in connection with the dissipation of heat from semiconductor chips or modules of electronic packages, and has even directed itself to providing heatsinks for pluralities of chips and modules, these are not always satisfactory due to the relatively rigid nature of the common heatsink which fails to take adequate cognizance of the physical mismatches and thermal expansion problems encountered by the discrete components of the electronic packages.
2. Discussion of the Prior Art
Sammakia et al. U.S. Pat. No. 6,058,015, which is commonly assigned to the assignee of the present application, discloses an electronic package wherein a stiffener ledge is equipped with a thermally conductive material which attaches a heatsink cover or lid portion to an adhesive on the stiffener ledge. This construction pertains to a heatsink for a single chip and is not adapted to provide for a common and compliant heatsink structure for multiple chips in a manner analogous to that of the present invention.
Dodge et al. U.S. Pat. No. 6,025,992, which is also assigned to the present assignee, discloses an integrated heat exchanger for a memory module in which a two-sided card is equipped with modules, and wherein a heatsink wraps around the opposite card surfaces. This does not provide for a type of heatsink structure which is common to a plurality of modules or semiconductor chips analogous to the present.
DiGiacomo et al. U.S. Pat. No. 5,981,310, which is assigned to the present assignee, although disclosing common heatsink structures for a module having a plurality of semiconductor chips, although disclosing a plurality of essentially compliant heatsinks, fails to provide a type of construction as disclosed by the present invention. This publication utilizes a heatsink which is constituted of a similar CTE (coefficient of thermal expansion) material as the substrate mounting the chips. Any heatsink compliance is only in a z-direction and does not enable compliance in other directions, such as in the x and y directions of a modular construction.
Sherif et al. U.S. Pat. No. 5,724,729 and U.S. Pat. No. 5,623,394, which are commonly assigned to the present assignee, each disclose an apparatus and method for cooling chips wherein different types of materials are interposed between a common heatsink and a plurality of discrete semiconductor chips over the extent of the various chip surfaces. These different thermally conductive adhesives facilitate a customized cooling of different types of chips, and do not provide for a common multi-directionally compliant heatsink structure for a plurality of semiconductor chips analogous to the inventive concept.
Alfaro et al. U.S. Pat. No. 5,650,915 discloses a thermally enhanced molded cavity package in which a single chip is provided with a heatsink. There is no disclosure of a compliant common heatsink structure for a multiple chips and modules analogous to that of the present invention.
Baker U.S. Pat. No. 5,003,429, which is assigned to the present assignee, discloses a solid common heatsink structure for a plurality of semiconductor chips in which any flexing or resilient deflection is only permitted at the leads of a modular construction. There is no disclosure of a compliant common heatsink structure for a plurality of chips and modules of an electronic package analogous to that of the present invention.
Romano"" U.S. Pat. No. 4,887,149 discloses a single chip heatsink construction having screw clamping attachments at the edge thereof so as to enable the positioning of the heatsink relative to the semiconductor chip. There is no disclosure of utilizing a common heatsink for multiple chips and modules in a compliant arrangement analogous to that of the present invention.
Finally, Butt et al. U.S. Pat. No. 4,849,857 discloses a heat dissipating interconnecting structure for a single chip heatsink device which in no manner can be utilized for a common heatsink incorporating the compliant features in a manner analogous to the present invention, in conjunction with a plurality of chips and modules for an electronic package.
In essence, none of the prior art publications currently utilized in the technology provide for a common heatsink for multiple chips and modules of an electronic package incorporating a compliant thermal interface and a minimizing of the effect caused by package tolerances.
In particular, pursuant to preferred embodiments of the invention, a common heatsink for a plurality of semiconductor chips or leaded components positioned on a substrate, such as a printed or wiring circuit card or the like, includes a common heatsink incorporating compliant structure intermediate the various or adjacent chips so as to enable essentially universal compliance between the various chips and the covering heatsink portion in x, y and z directions.
In that regard, pursuant to various embodiments, intermediate a plurality of semiconductor the chips or modules which are positioned on a single substrate of an electronic package, a common heatsink for all of the chips or modules may be either severed or provided with regions of reduced thicknesses so as to enable the heatsink to be imparted compliant characteristics which will facilitate compliance in z, x and y directions between each respective chip or module, thereby producing compliant interfaces while concurrently minimizing or eliminating the effects of package tolerances.
Pursuant to another aspect of the invention, there is provided a precision tool which may be employed to set the height between the top surfaces of adjacent chips and a flat-machined bottom cover ledge so as to enable to forming of precision adhesive gaps for removing heat effectively in the provision of a plurality of chips and a common heatsink. Accordingly, it is an object of the present invention to provide an arrangement comprising a common heatsink for multiple chips and modules of an electronic package.
Another object of the present invention resides in the provision of a common heatsink for multiple semiconductor chips and modules of a electronic package wherein the common heatsink includes a compliant configuration and thermal interface so as to minimize the effects of package tolerances.
Yet another object of the present invention is to imparting a method of providing compliant thermal interfaces to a common heatsink for an electronic package mounting multiple semiconductor chips and modules so as to compensate for manufacturing tolerances and thermal interfacing effects.
A further object of the present invention resides in the provision of a tool which will enable the formation of precision adhesive gaps between a plurality chips so as to remove heat effectively through the intermediary of a compliant common heatsink.
A still further object is to provide a method of utilizing a tool for forming precision gaps of an adhesive nature intermediate small semiconductor chips in a common heatsink so as to set the height between the top surface of the chips and a bottom cover ledge of the heatsink.
An additional object of the invention may be ascertained in that there is derived a decoupling of the common heatsink from the semiconductor chips and module components in the x- and y-directions so as to reduce any thermal coefficients stresses which may be generated in the electric package.